1. Field of the Invention
This invention relates to pipe lining techniques, and more particularly, to a branch pipe liner bag having a hardened flange at one end thereof for easy and reliable positioning, and a method of lining a branch pipe using the branch pipe liner bag.
2. Description of the Related Art
When an underground pipe, such as pipelines and passageways, becomes defective or too old to perform properly, the pipe is repaired and rehabilitated without digging the earth to expose the pipe and disassembling the sections of the pipe. This non-digging method of repairing an underground pipe has been known and practiced commonly in the field of civil engineering. The pipe lining method utilizes a tubular pipe liner bag made of a resin absorbent material impregnated with a hardenable resin, and having the outer surface covered with a highly air-tight plastic film. The tubular pipe liner bag is inserted into a pipe to be repaired by means of a pressurized air such that the pipe liner bag is turned inside out as it proceeds deeper in the pipe. Hereinafter, this manner of insertion shall be called "everting". When the entire length of the tubular liner bag is everted (i.e., turned inside out) into the pipe, the everted tubular liner bag is pressed against the inner wall of the pipe by a pressurized air, and the tubular flexible liner is hardened as the hardenable resin impregnated in the liner is heated, which is effected by heating the air filling the tubular liner bag. It is thus possible to line the inner wall of the defective or old pipe with a rigid liner without digging the ground and disassembling the pipe sections.
Generally, a main pipe of sewerage pipe lines or the like may have a plurality of branch pipes confluent, thereto, which can also be lined by a method similar to that mentioned above. An example of applying the above-mentioned method to a branch pipe is illustrated in FIG. 17.
FIG. 17 is a cross-sectional view illustrating a conventional branch pipe lining method, wherein a pressure bag 113 for eversion is inserted into a main pipe 110. Since this pressure bag 113 must be eventually separated from a branch pipe liner bag 101, a sealed tube 130 must be connected to the pressure bag 113 for applying a pressure to the branch pipe liner bag 101.
The pressure bag 113 is supplied with compressed air or the like, and the sealed tube 130 and the branch pipe liner bag 101 are inserted inside out into a branch pipe 111. With the illustrated state maintained, a hardenable resin impregnated in the branch pipe liner bag 111 is hardened. Then, the sealed tube 130 is pulled out of the branch pipe 111 (branch pipe liner bag 101), the inner wall of the branch pipe 111 is lined with the hardened branch pipe liner bag 111, thus repairing the branch pipe 111.
In the method mentioned above, however, a sealed tube of an appropriate length must be prepared for a branch pipe of a different-length each time a different branch pipe is repaired, thus requiring a replacement of a sealed tube for each branch pipe.
To solve the inconvenience mentioned above, a branch pipe lining method illustrated in FIGS. 18 and 19 has been previously proposed by the present inventors.
FIGS. 18 and 19 are cross-sectional views illustrating that previously proposed branch pipe lining method. In this method, an air-tight connection between a pressure bag 213 and a branch pipe liner bag 201 is provided by a tear-off tube 230, one end of which is temporarily bonded to the branch pipe liner bag 201. In these drawings, a guide tube 231 is disposed in a main pipe 210, and an air mat 232 is used to urge a flange 203 of the branch pipe liner bag 201 onto the inner wall surface of the main pipe 210. Also, an in-pipe work robot 212 has been introduced in the main pipe 210.
Specifically, as illustrated in FIG. 18, when a pressure bag 213 is supplied with compressed air with the flange 203 of the branch pipe liner bag 201 maintained pressed onto the inner wall of the main pipe 210, the branch pipe liner bag 201 is everted and inserted into the branch pipe 211 in a direction indicated by a white arrow by the action of the compressed air which applies a pressure to the branch pipe 21. When the branch pipe liner bag 201 has been completely inserted into the branch pipe 211 over the entire length thereof, a hardenable resin impregnated in the branch pipe liner bag 201 is hardened to line the branch pipe 211 with the hardened branch pipe liner bag 201, thus repairing the branch pipe 211.
After the branch pipe is lined as mentioned above, the pressure bag 23 is moved in a direction indicated by a horizontal arrow as illustrated in FIG. 19. Since the pressure bag 213 and the robot 212 are linked together by the-guide tube 231, the robot 212 is also moved in the same direction. The tear-off tube 230 temporarily bonded to the branch pipe liner bag 201 is torn off the temporarily bonded portion, and separated from the branch pipe liner bag 201.
Therefore, according to the method mentioned above, since the air-tight connection between the pressure bag 213 and the branch pipe liner bag 201 is provided by the tear-off tube 230, the same tear-off tube 230 can be used even if a branch pipe of a different length is to be lined, thus eliminating the replacement of the sealed tube 130 in the method illustrated in FIG. 17.
However, when the tear-off tube 230 is torn off, the tear-off tube 230 may not be completely removed from the branch pipe linear bag 201 with a portion thereof remaining on the inner wall of the branch pipe liner bag 201. The remaining portion of the tear-off tube 230 acts as unwanted flash which causes problems such as a deteriorated inner wall surface of the branch pipe 211, attachment of flowing substances within the branch-pipe 211 to the flash, and so on.